Percutaneous puncture treatment, in which a medical instrument, such as a needle, is guided to the affected part, is a typical example of minimally invasive treatment that is commonly performed. Examples of puncture treatments include ablation treatment in which a tumor or cancer cells are burned with radio waves and cryotherapy in which a tumor or cancer cells are frozen by using, for example, a freezing device or cooling gas. Puncture biopsy has also been commonly performed in pathological diagnosis based on tissue sampling.
In the medical environment, it is necessary to position a needle or multiple needles precisely inside tissue or a specific organ for accurate diagnosis or minimal invasive therapy. Biopsy, ablation, cryotherapy, aspiration and drug delivery are examples that require high precision needle placement and many of these treatments require the use of multiple needles in a treatment. Prior to a percutaneous incision, a target area of interest (e.g., tumor, nodule, etc.) is confirmed by means of non-invasive imaging with magnetic resonance imaging (MRI), ultrasound or other imaging modality. Once the target area of interest is positively determined, the clinician decides an entry point, inserting direction and depth to be reached by the needle. This process often requires a lengthy trial and error routine, which can be deleterious to the patient. Accordingly, in the last few decades there has been an increased interest in the development of needle guiding systems that can improve accuracy of needle positioning, minimize patient discomfort, and shorten time of operation.
To accurately position a needle with respect to a target, such as a tumor, in puncture treatment, an X-ray computed tomography (CT) unit, an MRI unit, etc., for acquiring medical images is used as a visualization unit for visualizing the needle. In puncture treatment in which such a modality is used as a visualization unit, it is often difficult to position the needle with respect to the target by a single puncturing process. Thus, the needle is generally guided to the target by acquiring medical images multiple times and correcting the insertion trajectory little by little in accordance with information from the acquired images. Accordingly, to reduce the operation time and burden on patients as well as patient's exposure to imaging radiation, various needle positioning apparatuses for positioning the needle to the target to provide a reduction in the number of times of corrections of the trajectory have been developed.
For example, U.S. Pat. No. 9,125,676 and U.S. Pat. No. 9,408,627 discloses a needle positioning apparatus having a cantilever arc guide structures with two ends attached to a base or support ring such that the guides are compliant against induced forces on both of the ends. The guides may experience large deformation forces during assembly. This assembly error in turn causes position inaccuracy. Furthermore, the guides have relatively low stiffness and do not maintain a precise position when subjected to force from the medical tool during guidance. Additionally, with respect to the apparatus of U.S. Pat. No. 9,125,676, a locking pin is used to maintain the arc guide perpendicular to the base plate. This causes large angle error because the fixing position is close to the triangle vertex of the angle, which increases an angular error with the small position error. Even when the locking pin is unlocked, the arc guide is free to rotate in the angular-error direction. Thus, whether locked or unlocked there is a large angular error. Also, the locking pin and fixing screws are small parts which are risky in a surgical context. Finally, the base plate of the U.S. Pat. No. 9,125,676 apparatus exposes the bearing surface for the arc guide to the external environment, which risks dust and fluid to enter during a medical procedure.
Thus, there is need for medical guide apparatus that avoids the above-noted problems.